Is the Purified Protein Derivative (PPD) test safe during pregnancy?

Safety of PPD Testing During Pregnancy

The Purified Protein Derivative (PPD) test is safe to administer during pregnancy, with no documented episodes of fetal harm resulting from its use. 1

Evidence Supporting Safety

• Thousands (perhaps millions) of pregnant women have undergone PPD skin testing with no documented episodes of fetal harm resulting from the tuberculin test 1
• Pregnancy should not exclude a female healthcare worker from being skin tested as part of a contact investigation or regular skin-testing program 1
• CDC guidelines explicitly state that pregnancy is not a contraindication to tuberculin skin testing 1

Indications for PPD Testing During Pregnancy

• PPD testing is indicated for pregnant women who:
  • Are at high risk for tuberculosis exposure 1
  • Have symptoms suggestive of active tuberculosis 1
  • Have known exposure to someone with active tuberculosis 1
  • Are HIV-positive or at increased risk for HIV infection 1

Interpretation of PPD Results in Pregnancy

• For pregnant women with HIV infection, ≥5 mm of induration is considered a positive reaction 1
• For pregnant women without HIV but with other risk factors, ≥10 mm of induration is considered positive 2
• For pregnant women with no risk factors, ≥15 mm of induration is considered positive 2

Management After Positive PPD Test in Pregnancy

• If a pregnant woman has a positive PPD test, a chest radiograph with appropriate abdominal/pelvic lead apron shielding should be performed to exclude active TB 1
• After active TB is excluded, chemoprophylaxis with isoniazid is recommended during pregnancy for those with a positive TST 1
• Some providers may choose to defer isoniazid preventive therapy until after the first trimester due to concerns about potential teratogenicity, though this is not explicitly required 1
• When preventive therapy is initiated during pregnancy, isoniazid should be accompanied by pyridoxine (vitamin B6) to reduce the risk of neurotoxicity 1

Important Considerations

• PPD reactivity is not affected by pregnancy itself, unlike some other conditions such as HIV infection that can cause anergy 1, 3
• Multiple puncture TB skin tests (e.g., Tine) are not recommended; the Mantoux method with intradermally injected 5 TU PPD should be used 1
• If anergy testing is performed alongside PPD testing (which is no longer routinely recommended), mumps and candida are appropriate control antigens 1

Common Pitfalls to Avoid

• Do not delay PPD testing in pregnant women who need it, as the test has been proven safe 1
• Do not confuse PPD testing (which is diagnostic) with BCG vaccination (which is contraindicated during pregnancy, especially in HIV-infected persons) 1
• Do not interpret a negative PPD test as definitively excluding TB, especially in immunocompromised patients, as false negatives can occur 1

In conclusion, PPD testing is safe during pregnancy and should be performed when clinically indicated without concern for adverse fetal effects.